SYNTHETIC DETERGENT BAR AND MANUFACTURE THEREOF

Abstract: A detergent composition which is suitable for making into bars for personal washing comprises: (a) 10-60 %wt of a synthetic, non-soap detergent; (b) 10-60 %wt of water-soluble material which is neither soap nor a non-soap detergent and which has a melting point in the range 40 DEG C to 100 DEG C; and (c) 5-50 %wt of water-insoluble material which is neither soap nor a non-soap detergent and which has a melting point in the range 40 DEG C to 100 DEG C. The content of water, if any does not exceed 20 %wt of the composition and better is less than 15 %wt. The materials (b) and (c) serve to give structure to the bars. The compositions can be prepared by melting together the above-mentioned components at a temperature of 50-100 DEG C, without the conventional energetic working. Desirably the molten mixture contains less than 20 %wt material, other than synthetic, non-soap detergent, which does not enter the liquid phase. The melt can be cast into bars or cooled, milled, plodded and stamped into bars.

Description: SYNTHETIC DETERGENT BAR AND MANUFACTURE THEREOF This invention relates to synthetic detergent bars and detergent compositions which can be shaped into bars. Washing bars can be classified into soap bars, mixed active bars containing a significant proportion of soap and thirdly synthetic detergent bars containing only a small proportion of soap or none at all. Conventional soap bars comprise a large proportion, typically 60-80% by weight, of fatty acid soap. Fatty acid soaps are selected to provide a balance of soluble and insoluble soaps which provide the required functional properties as regards lather formation and bar structure. Conventional soap bars are manufactured by milling, plodding and stamping a semi-solid mass of soap and other components. Bars are known which contain a mixture of soap and synthetic detergent where the amount of soap may be less than the amount of synthetic detergent but is nevertheless still a significant contributor to the content of the bar. In such bars, as in conventional soap bars, the content of soap especially the insoluble soap contributes to the structure and physical properties of the bar. The third category is synthetic detergent bars, often known as "Syndet" bars, in which there is no soap or only a small amount and the detergent active is mostly or wholly a synthetic, non-soap, detergent. Generally such bars contain a substantial proportion of material which is not a detergent and which serves to give structure to the bar. Such "structurants" are normally water- insoluble and include such materials as starch and kaolin. The bars frequently also contain a plasticiser: known plasticisers include stearic acid and cetyl alcohol. Known surfactants for Syndet bars include primary alkyl sulphates, alkyl ether sulphates, betaines, sarcosinates, sulphosuccinates and isethionates. These syndet bars containing no soap or only a small proportion of soap are traditionally produced by energetic working of a physical mix of structurant, plasticiser and surfactant, i.e. both the soluble and insoluble components, in a high shear mixer to an end point at which the product is not gritty. The mix is then formed into 'syndet' bars. The known process has several disadvantages in that the physical mixing step is performed batchwise and requires an energetic mixer. We have now found that by adopting a novel composition, syndet bars may be produced by a process which dispenses with the known energetic working step. In contrast with prior compositions and processes the invention relies on ingredients which are molten at conveniently accessible temperatures but which are above the temperatures normally encountered during use of "Syndet" bars. As a result the necessary intimate mixing of the ingredients of the bar can be accomplished by simple mixing while the bar composition is liquid rather than by relying on energetic working to achieve intimate mixing of a mixture of solids. Accordingly, the present invention provides a detergent composition which is, or can be shaped into, a synthetic detergent bar, the composition comprising: (a) 10-60% by weight of a synthetic, non-soap detergent, (b) 10-60% by weight of a water-soluble structurant which is neither soap nor a non-soap detergent and which has a melting point in the range 40-100°C, (c) 5-50% by weight of a water-insoluble structurant which is neither soap nor a non-soap detergent and which has a melting point in the range 40- 100°C, and (d) 0-20% by weight water. It is desirable that the content (if any) of material other than said synthetic non-soap detergent (a) which does not melt below 100°C is less than 20% by weight of the composition. In many embodiments of this invention the content of the synthetic detergent (a) will lie in the range 10 to 50% by weight. Preferably the composition will contain some water, in an amount from 3% or 5% to 20% better at most 15% by weight of the composition. It will be seen from the above, that a significant constituent of a composition according to this invention is a water-soluble material which melts at a temperature in the range 40-100°C and serves as a bar structurant. Such a material assists in giving the desired properties notably that the bar has a rigid solid form. It will also be noted from the above that the composition of the bar can tolerate the presence of some material which does not melt at temperatures below 100°C. Such material can also serve as a structurant. Such material is not an essential requirement and it may be entirely absent. If such material is present, the molten composition will not be fully liquid at temperatures of up to 100°C unless the non-melting material dissolves in the other materials present. We have found that a moderate amount of material which does not melt can be dispersed in the molten composition while it remains sufficiently liquid to be stirred without requiring energetic working. As will be mentioned again below, this material which disperses but does not melt may be at least part of the non-soap synthetic detergent (a) and/or material other than this category. Suitable synthetic detergents (a) are: alkyl ether sulphates; alkylethoxylates; alkyl glyceryl ether sulphonates; alpha olefin sulphonates; acyl taurides; methyl acyl taurates; N- acyl glutamates; acyl isethionates; anionic acyl sarcosinates; alkyl phosphates; methyl glucose esters; protein condensates,- ethoxylated alkyl sulphates; alkyl polyglucosides; alkyl amine oxides; betaines; sultaines,- alkyl sulphosuccinates, dialkyl sulphosuccinates, acyl lactylates and mixtures thereof. The above-mentioned detergents are preferably those based upon C 8 to C 24 , more preferably those based upon C 10 to C 18 , alkyl and acyl moieties. For many embodiments of this invention, the amount of synthetic detergent (a) may lie in the range from 10 to 50% wt . Further preferences are at least 20% and not more than 40%. Amongst the above synthetic detergents, some, notably acyl isethionates are less water-soluble than others. If a detergent of low solubility is used, it is preferably mixed with another synthetic detergent. Thus detergent compositions of this invention may possibly exclude acyl isethionate from the synthetic detergent (a) or may possibly include it jointly with other synthetic detergent. In some embodiments of this invention acyl isethionate is not more than 10% by weight of the composition e.g. 5% to 9.5%. However, further embodiments of the invention include larger quantities of acyl isethionate, e.g. up to 30% by weight of the composition. The water-soluble structurant (b) is required to melt in the temperature range from 40°C to 100°C so that it can be melted to form the bar composition but will be in a solid state at temperatures at which the bar will be used. Preferably it has a melting point of at least 50°C, notably in the narrower range from 50°C to 90°C. Materials which are envisaged as the water-soluble structurant (b) are moderately high molecular weight polyalkylene oxides of appropriate melting point and in particular polyethylene glycols or mixtures thereof. Polyethylene glycols (PEG's) which are used may have a molecular weight in the range 1500-10,000. However, in some embodiments of this invention it is preferred to include a fairly small quantity of polyethylene glycol with a molecular weight in the range from 50,000 to 500,000, especially molecular weights of around 100,000. Such polyethylene glycols have been found to improve the wear rate of the bars. It is believed that this is because their long polymer chains remain entangled even when the bar composition is wetted during use. If such high molecular weight polyethylene glycols (or any other water-soluble high molecular weight polyalkylene oxides) are used, the quantity is preferably from 1% to 5%, more preferably from 1% or 1.5% to 4% or 4.5% by weight of the composition. These materials will generally be used jointly with a larger quantity of other water-soluble structurant (b) such as the abovementioned polyethylene glycol of molecular weight 1500 to 10,000. Some polyethylene oxide-polypropylene oxide block copolymers melt at temperatures in the required range of 40 to 100°C and may be used as part or all of the water- soluble structurant (b) . Preferred here are block copolymers in which polyethylene oxide provides at least 40% by weight of the block copolymer. Such block copolymers may be used, in mixtures with polyethylene glycol or other water-soluble structurant. Preferably the total quantity of water-soluble structurant (b) is from 20% to 50% by weight of the composition. The water-insoluble structurants (c) are also required to have a melting point in the range 40-100°C, more preferably at least 50°C, notably 50°C to 90°C. Suitable materials which are particularly envisaged are fatty acids, particularly those having a carbon chain of 12 to 24 carbon atoms. Examples are lauric, myristic, palmitic, stearic, arachidic and behenic acids and mixtures thereof. Sources of these fatty acids are coconut, topped coconut, palm, palm kernel, babassu and tallow fatty acids and partially or fully hardened fatty acids or distilled fatty acids. Other suitable water- insoluble structurants include alkanols of 8 to 20 carbon atoms, particularly cetyl alcohol. These materials generally have a water-solubility of less than 5g/litre at 20°C. The relative proportions of the water-soluble structurants (b) and water-insoluble structurants (c) govern the rate at which the bar wears during use. The presence of the water-insoluble structurant tends to delay dissolution of the bar when exposed to water during use and hence retard the rate of wear. Preferably the total quantity of component (c) is from 10% to 40% by weight of the composition. A water-insoluble material which does not melt below 100°C can function as an additional bar structurant. It may be stipulated as a requirement that the content (if any) of water-insoluble material which does not melt below 100°C is less than 20% by weight of the composition. If a water-insoluble structurant (c) which does not melt below 100°C is present it may well be selected from plant materials or minerals. Starches, including corn starch, are preferred amongst the plant materials while kaolin and calcite are preferred mineral materials. The ratio of water-soluble structurant (b) to the total of water- insoluble structurants may possibly lie in a range from 2:3 or 1:1 up to 3:1 or 5:1. Some soap, that is to say salts of monocarboxylic fatty acids having chain lengths of 8 to 22 carbon atoms may be included in the bar compositions of this invention. The amount is desirably not greater than 10% by weight of the composition. We have found that if water-insoluble soap is included, it is advantageous in reducing the wear rate of the bars. Such water-insoluble soaps are salts of saturated fatty acids having chain lengths of 16 to 22 carbon atoms, especially 16 and 18. Preferably these salts are sodium salts. They melt at temperatures above 100°C and therefore come within a category (e) which is material, other than synthetic detergent, melting above 100°C. If water-insoluble soap is present in the composition, the amount of it desirably does not exceed 10% by weight of the composition, for example lying in a range from 3% to 9.5% by weight, more preferably 5% to 9%. It is preferred to include a combination of polyethylene glycol with molecular weight 50,000 to 500,000 as at least part of the soluble structurant (b) and water- insoluble soap as at least part of the insoluble material (c) . Use of these materials in combination has been found to improve wear rate of the bars, while also giving them a good feel when handled during use. When such a combination of materials is used, the preferred amounts, by weight of the composition are: 4 to 9.5% of water-insoluble soap and 1.5 to 4.5% polyethylene glycol with molecular weight in the range from 50,000 to 500,000. Materials which may be included but which do not melt at temperatures below 100°C can be classified as non-soap synthetic detergent which does not completely liquify at temperatures below 100°C, for example acyl isethionates; soap, especially water-insoluble soap, which does not melt below 100°C; other water-insoluble materials which do not melt below 100°C. Materials, other than synthetic detergent, which are water-soluble but do not melt below 100°C are preferably absent, or present only in quantities which are small such as not more than 10% better not more than 5% by weight of the composition. It is desirable that the total quantity of material in the second and third of these categories (i.e. materials other than non-soap synthetic detergent) is not more than 20% by weight of the composition. The total quantity of material which does not melt below 100°C should not exceed 50% by weight of the composition, preferably less, such as not more than 40% or not more than 30%, or even 20% and should not be so much that the molten composition ceases to be stirrable. Bar compositions of this invention will usually contain water, but the amount of water is only a fairly small proportion of the bar. Larger quantities of water reduce the hardness of the bars. Preferred is that the quantity of water is not over 15% by weight of the bars, e.g. lying in a range from 3% or 5% to 14.9% by weight. Bars of this invention may optionally include so-called benefit agents - materials included in relatively small proportions which confer some benefit additional to the basic cleansing action of the bars. Examples of such agents are: - skin conditioning agents, including emollients such as fatty alcohols and vegetable oils, essential oils, waxes, phospholipids, lanolin, anti-bacterial agents and sanitisers, opacifiers, pearlescers, electrolytes, perfumes, suncreens, fluorescers and colouring agents. Preferred skin conditioning agents comprise silicone oils, mineral oils and/or glycerol . According to a further aspect of the present invention there is provided a process for the manufacture of synthetic detergents bars rfhich comprises the steps of : (i) preparing a liquid mixture of the synthetic, non- soap detergent, the structurants and optionally water at a temperature of 50°C to 100°C, preferably 50°C to 90°C, said mixture comprising less than 20%wt of material other than synthetic non-soap detergent which does not enter the molten liquid phase, (ii) cooling the product of step (i) to a temperature at which it solidifies, and (iii) forming the product of step (i) into bars. The liquid mixture can be a single or multiple phase system. The single phase can be an isotropic mixture whereas the multiple phase system can comprise either an emulsion or liquid crystal dispersion. The mixture can be prepared by mixing of the components followed by heating of the mixture to the molten state when further mixing will occur, or by heating of the components followed by mixing of the components. Step (i) may be carried out in a stirred, heated vessel. For a composition which contains fatty acid or a mixture of soap and fatty acid and also contains polyalkylene oxide, a useful procedure begins with melting the fatty acid in a heated vessel with a stirrer. The stirrer is started, and the polyalkylene oxide is added. At this stage any soap is made in situ by partial neutralisation of the fatty acid. Next the non-soap detergent is added. The end result is a macroscopically homogenous molten mixture, with not more than 50% solids present. Preferably step (ii) is carried out on a chilled, scraped roller which may be part of a chilled mill. Minor ingredients and benefit agents can be added at this stage, between steps (ii) and (iii) . Step (iii) can comprise milling, plodding and stamping, or optional milling followed by compression of the material into a bar shape. In an alternative embodiment of the invention the liquid mixture from step (i) is cast into moulds. The casting step can be employed to form a log which is further processed into bars or to form bars directly. Where the product is cast into bars the process steps (ii) and (iii) are combined; the moulds which are used can form the final packaging of the bars or the bars can be extracted from the moulds and re-packaged. In order that the present invention may be further understood it will be described with reference to the following illustrative examples. EXAMPLE 1 Components as listed in Table 1 below were melted together at 80°C to produce a material consisting predominantly of a liquid phase. All amounts are given in percentages by weight . On cooling to room temperature, solid, generally cuboid bars were formed from compositions (A) and (B) using a single bar press. Identical compositions were also formed into bars by using a casting process from the hot melt. TABLE 1 A B SLES 3EO * 21% 21% Stearic Acid 10% 20% Cetyl alcohol 10% - PEG 4000" 50% 50% Water 8% 8% Perfume 1% 1% * SLES 3EO denotes sodium lauryl ether sulphate with average 3 ethylene oxide residues. ** PEG 4000 denotes polyethylene glycol with mean molecular weight 4000. Both the melt-cast and pressed bars had acceptable properties for 'syndet' bars. EXAMPLE 2 The materials listed in Table 2 below, where all amounts are given as percentages by weight, were melted together at 80°C to produce a pumpable, stirrable liquid. The liquid melt was poured into bar shaped moulds and allowed to cool to form solid bars, i.e. the bars were cast from the melt. Acceptable bars were obtained. TABLE 2 2A 2B 2C 2D Aerosol OT * 21 45 25 50 PEG 4000 37 25 37.5 25 Stearic acid 37 25 37.5 25 Water 5 5 0 0 Aerosol OT is dioctylsulphosuccinate EXAMPLE 3 The materials listed in Table 3 below were melted together at 80°C to produce a pumpable, stirrable liquid. All amounts are given in percentages by weight . The liquid melt was cast into bars as in Example 2. A quantity of each melt was processed into bars by a different route. The melt was cooled by passing over a chilled three-roll mill. Small quantities of perfume, opacifier and fluorescer were added, totalling less than 2% by weight of the composition. The resulting composition was re-milled, passed through a vacuum plodder and stamped into the desired bar shape using a manual press . TABLE 3 3A 3B 3C 3D SLES 3EO 14 21 28 14 PEG 4000 40 35 30 53 Stearic acid 40 35 30 27 Water 6 9 12 6 Acceptable bars were obtained by both processing routes. EXAMPLE 4 Components as listed in Table 4 below were made into bars by the procedure of Example 2. All amounts are given in percentages by weight . These bars contained a mixture of two detergent actives. TABLE 4 4A 4B 4C 4D 4E 4F 4G 4H 4J 4K 4L 4M 4N 4P 4Q 4R SLES 3E0 27 20 14 27 20 14 27 20 14 27 20 14 7 20 17 10 Aerosol OT 4 3 2 - - - - - - - - - 10 30 25 15 Tallow 20EO * - - - 4 3 2 - - - - - - - - - - DEFI" - - - - - - 4 3 2 - - - - - - - CAPB" * - - - - - - - - - 4 3 2 - - - - PEG 4000 38 46 52 38 46 52 38 46 52 38 46 52 56 20 25 20 Stearic Acid 19 23 26 19 23 26 19 23 26 19 23 26 24 20 25 50 Water 12 8 6 12 8 6 12 8 6 12 8 6 3 10 8 5 Fatty alcohol with mixed 16 and 18 carbon atom chain lengths, ethoxylated with an average of 20 ethylene oxide residues. ** Directly esterified fatty acyl isethionate, which is a mixture containing about 70% by weight of fatty acyl isethionate, 15-20' fatty acid and small quantities of other materials, ex Lever Brothers, USA *** Cocoamidopropyl betaine, ex Albright and Wilson, UK. EXAMPLE 5 The materials listed in Table 5 below were made into bars by the procedure of Example 2. All amounts are given in percentages by weight. In these bars, the water-soluble structurant was a mixture of polyethylene glycol and a block copolymer of polyethylene oxideand polypropylene oxide, available as Pluronic F87, ex BASF Germany. TABLE 5 5A 5B Aerosol OT 21 45 PEG 4000 20 20 Pluronic F87 17 5 Stearic acid 37 25 Water 5 5 EXAMPLE 6 The materials listed in Table 6 below were melted together at 80°C. All amounts are given in percentages by weight. The PEG 4000 and stearic acid were the first materials to be heated and melted. When these were molten, a small quantity of sodium hydroxide was added to neutralise a little of the stearic acid to sodium stearate. After this the remaining materials were added and stirred to produce a pumpable, homogeneous liquid. Each melt was cooled by passing over a chilled three- roll mill. 1% of perfume, and 0.3% of titanium dioxide as opacifier were then added, followed by milling and plodding the resulting composition and stamped into the desired bar shape using a manual press. TABLE 6 6A 6B 6C 6D SLES 3EO 11 11 10 10 DEFI 18 33 20 20 CAPB 1 5 1 1 PEG 4000 35 25 36 36 PEG 100,000 4 4 0 8 Stearic acid 22 13 20 20 Sodium stearate 4 4 8 0 Water 5 5 5 5 EXAMPLE 7 The materials listed in Table 7 below were made into bars by the procedure of Example 3 in which the melt was cooled on a mill, plodded and stamped into bars. All quantities are given as percentages by weight . These bars contained a mixture of three detergent actives. TABLE 7 7A 7B 7C 7D 7E 7F SLES 3E0 10 9.56 9.22 10.42 9.96 9.6 DEFI 17 16.2 15.68 31.26 29.87 28.83 CAPB 1 0.96 0.92 4.72 4.53 4.37 PEG 4000 33 31.53 30.43 23.68 22.63 21.84 PEG 100,000 4 3.82 3.69 3.8 3.62 3.5 Stearic acid 21 20.1 19.37 12.32 11.77 11.36 Sodium 4 3.82 3.69 3.8 3.62 3.5 stearate Water 10 14 17 10 14 17 Compositions 7C and 7F gave compositions which were too soft to process whereas the remaining compositions could be processed into firm bars . Example 8 A number of compositions from the preceding examples were assessed for mildness using a zein test generally as described by Gotte, Proc. Int. Cong. Surface Active Subs., 4th, Brussels, 3., 89-90 (1964) . The test determines the amount of amino acid solubilised from zein under specified conditions. The solubilised material is determined by a nitrogen assay. The results were as follows. Composition number Solubilised nitrogen 3A 0.08 3B 0.13 3C 0.16 4D 0.11 4G 0.1 4K 0.11 6A 0.12 6C 0.05 6D 0.05 7D 0.2 80/20 coconut/tallow soap 0.73 'DOVE' commercial 0.22 'syndet'bar based on DEFI The low values of zein solubilisation for the bars of this invention indicate very good mildness.

Claims: CLAIMS : 1. A detergent composition comprising: (a) 10-60%wt of a synthetic, non-soap detergent, (b) 10-60%wt of water-soluble material which is neither soap nor a non-soap detergent and which has a melting point in the range 40°C to 100°C, (c) 5-50%wt of water-insoluble material which is neither soap nor a non-soap detergent and which has a melting point in the range 40°C to 100°C, and (d) 0-20%wt of water. 2. A detergent composition according to claim 1 wherein the quantity of component (a) is 10 to 50%wt. 3. A detergent composition according to claim 1 or claim 2 wherein the quantity of water is 5 to 14.9%wt. 4. A detergent composition according to any one of claims 1 to 3 wherein the content of material, other than said synthetic non-soap detergent, which does not liquefy below 100°C is less than 20%wt of the composition. 5. Detergent composition according to any one of claims 1 to 4 wherein component (b) comprises one or a mixture of polyethylene glycols having molecular weight from 1500 to 10 , 000 . 6. Detergent composition according to any one of claims 1 to 5 wherein component (b) includes polyethylene glycol having molecular weight 50,000 to 500,000 in an amount which is 1 to 4.5% by weight of the composition. 7. Detergent composition according to any one of claims 1 to 6 wherein component (c) is selected from the group consisting of lauric, myristic, palmitic, stearic, arachidic and behenic acids and mixtures thereof. 8. Detergent composition according to any one of claims 1 to 7 which comprises water-insoluble soap in an amount from 3% to 10% by weight of the composition. 9. A detergent composition according to claim 1 which is in bar form. 10. A process for the manufacture of a synthetic detergent bar which comprises the steps of : (i) preparing a liquid mixture comprising (a) 10-60%wt of a synthetic, non-soap detergent, (b) 10-60%wt of water-soluble material which is neither soap nor a non-soap detergent and which has a melting point in the range 40°C to 100°C, (c) 5-50%wt of water-insoluble material which is neither soap nor a non-soap detergent and which has a melting point in the range 40°C to 100°C, and (d) 0-20%wt of water; (ii) cooling the product of step (i) to a temperature at which it solidifies, and (iii) forming the product of step (i) into bars.

Inventors: CHAMBERS JOHN GEORGE, JOY BRYAN STUART, CHAMBERS, JOHN, GEORGE, JOY, BRYAN, STUART
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1994
Main classification: C11D17
IPC codes: C11D3, C11D17